PostgreSQL获取表的Size

最新推荐文章于 2025-03-10 11:54:49 发布

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最新推荐文章于 2025-03-10 11:54:49 发布

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文章标签：数据库

原文链接：https://my.oschina.net/mj23/blog/826614

本文提供了两个实用的SQL查询案例，帮助读者深入理解如何通过SQL高效地获取数据库表的空间使用情况及平均每行数据大小等关键信息。

为什么80%的码农都做不了架构师？>>>

SQL文1：

SELECT relname, reltuples, (relpages / 128) as mbytes, (relpages * 8192.0 / (reltuples + 1e-10)) as average_row_size FROM pg_class ORDER BY mbytes DESC;

SQL文2：

SELECT pgn.nspname, relname, pg_size_pretty(relpages::bigint * 8 * 1024) AS size, CASE WHEN relkind = 
't' THEN (SELECT pgd.relname FROM pg_class pgd WHERE pgd.reltoastrelid = pg.oid) WHEN nspname = 
'pg_toast' AND relkind = 'i' THEN (SELECT pgt.relname FROM pg_class pgt WHERE SUBSTRING(pgt.relname 
FROM 10) = REPLACE(SUBSTRING(pg.relname FROM 10), '_index', '')) ELSE (SELECT pgc.relname FROM 
pg_class pgc WHERE pg.reltoastrelid = pgc.oid) END::varchar AS refrelname, CASE WHEN nspname = 
'pg_toast' AND relkind = 'i' THEN (SELECT pgts.relname FROM pg_class pgts WHERE pgts.reltoastrelid = 
(SELECT pgt.oid FROM pg_class pgt WHERE SUBSTRING(pgt.relname FROM 10) = REPLACE(SUBSTRING(pg.relname 
FROM 10), '_index', ''))) END AS relidxrefrelname, relfilenode, relkind, reltuples::bigint, relpages 
FROM pg_class pg, pg_namespace pgn WHERE pg.relnamespace = pgn.oid AND pgn.nspname NOT IN 
('information_schema', 'pg_catalog') ORDER BY relpages DESC;

转载于:https://my.oschina.net/mj23/blog/826614